Regulating cannabis for non-medical, non-scientific uses is plainly disallowed by the UN drug conventions. Nevertheless, sub-national and national jurisdictions are choosing to formally regulate adult-use cannabis, through state-level ballot initiatives and legislation, as has been occurring in the United States since 2012, or through new national laws, as in Uruguay in 2013, and as in Canada, where bills are currently under parliamentary consideration. Such reforms pose considerable challenges to the international legal framework for drug control. This side event explored options for how countries might move forward with cannabis regulatory systems with due respect for international law.